Kava-kava extract, process for the production thereof and use thereof

ABSTRACT

Dry extract from kava-kava drug having a total content of kava lactones of at least 50% by weight and a flavokawin content of at the most 0.3% by weight. The extract is distinguished by good water solubility and high bioavailability after oral administration. To increase the kava lactone content in the extract and decrease the flavokawin content, a process is proposed in which the raw extract is brought into solution and the content of flavokawins diminished by cold precipitation or by solvent distribution, whereafter the solution is concentrated to dryness. Drugs are made using the dry extract.

The invention relates to an extract of low flavokawin content from therhizome of Piper methysticum Forst. (pepper intoxicant, Piperaceaefamily) called "kava-kava", having a high content of kava lactones andgood bioavailability.

In Polynesia, the home of the kava bush, since ancient times the nativeshave used an aqueous extract (cold macerate) of the drug for ritual andtherapeutic purposes.

The relaxing action of the drug, which is used as phytotranquilizer forrelaxing in cases of nervousness and overexcitement and as an agent forincluding sleep, is based on the occurrence of several 6-substituted4-methoxypryones, that is the kava lactones kawain, dihydrokawain,methysticin, dihydromethysticin, yangonin and desmethoxyyangonin (cf.Hansel et al., Deutsche Apothekerzeitung 125, No. 41, pages 2056-2058(1985)). In addition, in the kava drug the yellow compounds flavokawin Aand flavokawin B are contained to which skin-specific secondary effectsare assigned (Shulgin, Bulletin on Narcotics, Vol. XXV, No. 2, pages59-74 (1973)). Finally, the drug contains a series of further contentswhich have not yet been fully clarified and which are pharmacologicallyinert and referred to as "matrix substances".

Some kava lactones have also been synthesized, including kawain, theracemate being available commercially as psychopharmacological agent inthe form of capsules containing 200 mg of the active agent.

The kava lactones are practically insoluble in water. For example, themaximum solubility of kawain at 21° C. is 2.2 mg/100 ml water. In thecold macerate used by the Polynesians, however, there is up to about 70mg kava pyrones (total pyrone content) in every 100 ml macerate. It wasconcluded from this that the pharamacologically inert "matrixsubstances" contained in the drug act as solubilizers for the kavapyrones (cf. Hansel et al., loc. cit.).

Because of its low bioavailability, the therapeutic effect obtainablewith the kava lactone preparations hitherto on the market isunsatisfactory. The individual pure substances, irrespective of whetherthey are synthesized or isolated from the drug, must be administered inhigh doses because of their poor solubility whilst the dry extractsrecovered from the drug have a total lactone content of only about 5 to30% by weight so that in spite of the better solubility compared withthe pure substances high doses must again be used to obtain the desiredminimum titer in the blood or plasma.

The invention is therefore based on the problem of providing a dryextract having a substantially higher total lactone content butnevertheless good water solubility, with high bioavailability after oraladministration and as low a flavokawin content as possible, as well as asimple process for the production thereof. The invention is furtherbased on the problem of making pharmaceutical preparations with a highcontent of readily soluble and bioavailable kava lactones and as low aspossible in flavokawin content, which can be administered orally andwith which the danger of secondary effects due to discolouring of theskin is greatly reduced compared with the preparations known hitherto.

This problem is solved according to the invention by a dry extract fromthe rhizome of Piper methysticum Forst. which is characterized by atotal content of kava lactones of at least 50% by weight and aflavokawin content of at the most 0.3% by weight. Preferably, the dryextract has a total content of kava lactones of 50 to 90% by weightand/or a flavokawin content of less than 0.3% by weight. An extract isparticularly advantageous which has a total content of kava lactones of60 to 80% by weight and the flavokawin content of which is less than0.2% by weight.

Although the extract according to the invention is highly enrichedcompared with the extracts known hitherto and has a total content ofkava lactones of up to 90% by weight and thus comes very close to thepure preparations, consisting for example of 100% kawain, it hassurprisingly been found that the bioavailability of the extractaccording to the invention is substantially better, both compared to thedry extracts known hitherto and compared to the pure substances hithertoused as pharmaceutical preparations, although it has been possible toreduce the pharmacologically inert matrix content to 20% by weightwhilst in the extracts known hitherto it was at least 70% by weight.

The dry extract according to the invention can therefore advantageouslybe employed for producing pharmaceutical preparations, in particularphytopharmaca, because to obtain the same pharmacological effect asmaller dosage than was necessary with the agents known hitherto issufficient. As clinical tests have shown, the effective daily dose isabout 300 mg of the extract according to the invention, corresponding toabout 50 mg pure kawain, whilst the effective daily dose of kawainadministered as pure substance is about 200 mg (cf. Kretschmer "Kavainals Psychopharmakon", MMW 4/1970, page 154-158).

The dry extract according to the invention can be prepared in simplemanner in that the pulverized rhizome of Piper methysticum Forst.(rhizoma kava-kava) is extracted with a suitable solvent such asacetone, chloroform, ethyl acetate, low alkanols having 1 to 4 C atomsor at least 50% by weight mixtures thereof with water and the extractsolution concentrated to dryness. The extraction can be carried out inthe form of a percolation or a multistage agitating or vortex extractionat room temperature or at elevated temperature. Depending on the solventused the raw extracts thus obtained have a content of kava lactones ofabout 50 to 70% by weight.

Thereafter, the raw extracts are again brought into solution andpurified by cold precipitation from solvents miscible with water, inparticular ethanol and acetone, or by solvent dispersion between anaqueous, aqueous-alcoholic or aqueous-acetonic first phase and a secondphase not miscible with said first phase, the second phase being anorganic phase formed from organic solvents such as chloroform, heptane,hexane, acetic acid ethyl ester and the like as well as mixturesthereof. The total content of kava lactones in the pure extracts thusobtained compared with the starting materials is only slightly reducedwhilst the flavokawin content is drastically reduced to a third to afifth of the starting content.

In the cold precipitation, as solvent firstly an organic solventmiscible with water is used, such as ethanol or another low alkanol oracetone, and the concentrated solution is mixed with water or with analkanol-water mixture until a milky clouding occurs, thorough mixingbeing carried out, whereafter the mixture is cooled, preferably to 5° to10°, and possibly allowed to stand for several hours, preferably about12 to 24 hours. Thereafter the deposited precipitate is separated andthe supernatant concentrated to dryness.

When using solvent dispersion the starting materials are eitherdissolved in an organic solvent not miscible with water, for examplechloroform, hexane heptane or an acetic acid ethyl ester/hexane mixture,whereafter said organic phase is extracted in portions by shaking withsmall amounts of an aqueous, aqueous-alcoholic or aqueous-acetonicphase, for example water, ethanol/water or acetone/water. Alternatively,the starting materials are dissolved in an organic solvent miscible withwater, for example ethanol or acetone, and the phase which isaqueous-alcoholic or aqueous-acetonic after addition of water isextracted several times by shaking or stirring with small amounts of anorganic solvent not miscible with water.

In every case the kava lactones are in the aqueous, aqueous-alcoholic oraqueous-acetonic phase whilst the flavokawins concentrate in the organicphase immiscible with water and can be removed by separating saidorganic phase.

The pure extracts are of syrupy, oily or resinous consistency. For themanufacture of tablets, dragees or capsules they are mixed with usualauxiliary substances, for example finely dispersed silicic acid such asaerosil, and vacuum dried.

The invention will be explained in further detail with the aid of thefollowing examples of embodiment. In the drawings:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show substance distribution diagrams which will beexplained in detail in conjunction with example 2,

FIGS. 3 and 4 show diagrams which represent the time profile of theplamsa level of methysticin and dihydromethysticin in a dog, and

FIG. 5 is a three-dimensional representation of the Hamilton anxietyscore with placebo comparison.

EXAMPLE 1 a) Extraction with acetone

1 kg ground kava-kava drug is mixed with 5 times the amount by weight ofacetone, homogenized and transferred to an extraction flask. Refluxextraction is carried out at 60° C. water bath temperature for 1 hour.After cooling the extract solution is filtered through a folded filter.The filtrate is concentrated to dryness (oily) in a rotary evaporator at60° C. water bath temperature. The filtration residue may possibly bepressed out and extracted again.

The yield is 27.68 g oily extract with a 66% content of kava lactones.

b) Depletion of yellow dyes (flavokawins) by combination of solvent/coldprecipitation

5 g of the kava extract obtained by the extraction described above iscompletely dissolved in 100 ml ethanol (96%) (A). Furthermore, 10 g ofthe kava extract is completely dissolved in 100 ml acetone (B).

20 ml of each of these starting solutions are diluted with water to 50ml, a milky colouring occurring.

The aqueous dilutions are cooled for 12 hours to 5° to 10° C.

Thereafter, clarification is carried out by centrifugation or filtrationand the kava lactones and flavokawins determined in the supernatant ofthe precipitation.

                  TABLE 1                                                         ______________________________________                                                        Content after solvent/                                        Starting content                                                                              cold precipitation                                            ______________________________________                                        kava lactones                                                                             100%    93% (A)                                                   flavokawins 100%    27% (A)                                                   kava lactones                                                                             100%    87% (B)                                                   flavokawins 100%    20% (B)                                                   ______________________________________                                    

Under these conditions a precipitation and depletion of the flavokawinsto about 20% of the starting value takes place. The loss of kavalactones is about 10%.

EXAMPLE 2 a) Extraction with 95% ethanol

500 g ground kava-kava drug is mixed with 4000 g 95% ethanol,homogenized, transferred to an extraction flask and extracted for 1 hourat 60° C. water bath temperature. After cooling filtration is carriedout through a suction filter. The drug residue is extracted again in thesame manner and filtered. The extract solutions were combined andconcentrated to dryness in a rotary evaporator at 60° water bathtemperature.

Yield: 28.88 g kava extract with a 43% content of kava lactones.

b) Depletion of yellow dyes (flavokawins) by solvent distribution

Saturated solutions of the kava extract thus obtained are prepared in 30ml of a mixture of 5 parts by volume acetic acid ethyl ester and 25parts by volume n-hexane.

These batches are each extracted by shaking 3 times with 30 mlethanol/water (ethanol content between 20 to 50% (v/v)).

In the ethanol/water phase or the hexane/acetic acid ester phase theamounts of kava lactones and flavokawins are determined by HPLCanalysis.

FIG. 1 depicts the proportion of compound groups in theethylacetate/hexane phase after extraction (three times) with an equalvolume of ethanol/water. FIG. 2 depicts the proportion of compoundgroups in the ethanol/water phase.

It can be seen from the diagrams of the substance distribution (FIGS. 1and 2) that in particular with an ethanol content of 30 to 40% theflavokawins are depleted to less than 20% of the starting value. Underthese conditions more than 70 to 80% of the kava lactones are recovered.

EXAMPLE 3 a) Extraction with chloroform

500 g kava-kava drug is reflux extracted with 10 times its amount byweight chloroform in a 6 l three-necked flask by stirring for 2 hours.

After cooling suction filtering is carried out through a large suctionfilter. The drug residue is extracted another 2 times in the samemanner. The chloroform extract solutions are combined and concentratedto an oily consistency in a rotary evaporator at about 50° C. bathtemperature.

Yield: 12.90 g kava extract with a 63% content of kava lactones

b) Depletion of yellow dyes (flavokawins) by solvent distribution

From the kava extract thus obtained saturated solutions in 50 mlethanol/water mixtures in each case are prepared (about 1-2 g, each).

These batches are extracted 3 times each with the same volume of hexaneor heptane. The contents of kava lactones and flavokawins are determinedin the ethanol/water phase or the hexane phase. The product phase(EtOH/water) has the contents of kava lactones and flavokawins indicatedin Table 2 (related to the starting extract in each case):

                  TABLE 2                                                         ______________________________________                                                       kava lactones                                                                           flavokawins                                          ______________________________________                                        ethanol/H.sub.2 O                                                                       85:15 (v/v)                                                                              83%         54%                                          ethanol/H.sub.2 O                                                                       70:30      85%         40%                                          ethanol/H.sub.2 O                                                                       50:50      73%          8%                                          ______________________________________                                    

It is apparent that with an ethanol content between 50 and 70% apronounced depletion of the flavokawins occurs with an acceptable lossof kava lactones.

EXAMPLE 4 Depletion of flavokawins by distribution between acetone/waterand heptane

An acetonic extract prepared according to Example 1 is concentrated todryness and thereafter dissolved again in 55% by weight acetone/water togive a solution with 4% dry residue. This solution is extracted in a4-stage mixer settler in counterflow with the same amount by volume of amixture of 8 parts heptane and 2 parts acetone.

The analyses values found in the dry residue of the acetone/water phaseare compared below with the starting values:

    ______________________________________                                                         kava lactones                                                                          flavokawins                                         ______________________________________                                        starting values    67.63%     1.89%                                           (extract without heptane/acetone                                              extraction)                                                                   acetone-water phase                                                                              70.66%     0.17%                                           ______________________________________                                    

The invention will be further explained below with regard to thepharmacokinetic properties of the kava extracts and the pharmaceuticalpreparations prepared therefrom:

The bioavailabilities of kava lactones in a dog are compared with eachother after administration of the extract prepared according to theinvention, a commercially usual extract and a mixture of the kavalactones as pure substances.

The extract prepared according to the invention was mixed with a galenicauxiliary substance (silicon dioxide) and administered in the form of acapsule; the commercially usual extract mixed with a galenic auxiliarysubstance (silicon dioxide) was administered in the same manner. Themixture of the kava lactones was in equal parts, as with the extractmade according to the invention, and administration was also as capsule.The dosage can be seen in Table 3.

                  TABLE 3                                                         ______________________________________                                                 Extract prepared                                                                           Mixture of                                                                              Dosage (mg/kg)                                         according to the pure  commercially                                  Lactone  the invention                                                                              substances                                                                              prepared extract                              ______________________________________                                        Kawain   1.23         1.23      1.23                                          DH-Kawain                                                                              1.43         1.43      1.34                                          Methysticin                                                                            1.14         1.14      1.25                                          DH-Methy-                                                                              1.23         1.23      1.30                                          sticin                                                                        Yangonin 0.82         0.82      0.94                                          ______________________________________                                    

Blood was taken at the following times after administration: 10, 20, 40,60, 120, 180, 240 and 360 minutes. The kava lactones were determined inthe plasma by HPLC.

FIGS. 3 and 4 depict the plasma levels of methysticin andDH-methysticin, respectively, after administration of the extracts andthe pure compounds, wherein line A is the extract produced according tothe invention, line B is a commercially available extract, and line C isa mixture of the lactones".

The following AUC-values¹) (0-6 h) were found in each case in five dogs(mean values±standard deviation) (Table 4):

                  TABLE 4                                                         ______________________________________                                                    Extract made  AUC (ng/ml · min)                                      according to  Mixture of the pure                                 Lactone     the invention substances                                          ______________________________________                                        Kawain      22210 ± 5862                                                                             --                                                  DH-Kawain.sup.2)                                                                          4144 ± 4134                                                                              --                                                  Methysticin  26598 ± 13956*                                                                           4907 ± 3329                                     DH Methysticin.sup.2)                                                                      58534 ± 12626**                                                                         20686 ± 9334                                     Yangonin    --            --                                                  ______________________________________                                         --Plasma level below the detection limit (about 30 ng/ml lactone)             Significance level                                                            *p < 0.05                                                                     **p < 0.01                                                                    .sup.1) AUC = area under the curve, calculated by the trapezium rule (cf.     Derendorf, Garret, "Pharmakokinetik", Wissenschaftliche                       Verlagsgesellschaft mbH, Stuttgart 1987                                       .sup.2) DH = dihydro                                                     

It was found that only the extract prepared according to the inventionled to a measurable absorption of kawain and DH-kawain. The absorptionof methysticin and DH-methysticin are significantly better with theextract prepared according to the invention.

In Table 5 the AUC values of four dogs are enumerated which received incrossover in each case the extract prepared according to the inventionand a commercially usual extract.

                  TABLE 5                                                         ______________________________________                                                              AUC                                                               Animal extract                                                                            (ng/ml · min)                                            prepared    commercially                                                      according   prepared                                                          to the invention                                                                          extract*    Quotient                                    Substance A           B           AUC.sub.A /AUC.sub.B                        ______________________________________                                        Kawain  1     32,080      30,855    1.04                                              2     19,540      24,430    0.80                                              3     22,710      17,325    1.31                                              4     19,590      18,303    1.07                                      DH-Kawain                                                                             1      4,200      --        --                                                2     --           3,970    --                                                3      2,700       4,226    0.63                                              4     11,020       1,153    9.56                                      Methysticin                                                                           1     51,070      30,826    1.66                                              2     22,320      12,476    1.79                                              3     21,810       7,620    2.86                                              4     22,080       9,275    2.38                                      DH-     1     76,480      58,496    1.31                                      Methysticin                                                                           2     52,830      41,962    1.26                                              3     63,720      21,762    2.93                                              4     57,040      33,267    1.71                                      ______________________________________                                         *standardized to the same dosage                                         

A comparison was made of the relative bioavailability of the extractaccording to the invention and the commercially usual extract with theaid of the bioavailability quotients (quotient AUC_(A) /AUC_(B)).Bioequivalence is the term used when the 95% confidence interval of thebioavailability quotients lies between 0.8 and 1.20 or when 3/4 of thevalues lie between 0.75 and 1.25 (cf. H. Blume,"Bioaquivalenz-Beurteilungsgrundlage fur Generika", PharmazeutischeZeitung 132, No. 4, pages 151-162 (1987)).

For methysticin and DH-methysticin all the bioavailability quotients areoutside the range of 0.75 and 1.25 and on the average are 2.17 and 1.80respectively. This means that the better bioavailability of the extractprepared according to the invention compared with the commercially usualextract is proved by recognized criteria. An example is the plasmalevels of methysticin and DH-methysticin after administration of thedifferent extracts or pure substances to a dog.

In the case of kawain identical absorption after administration of thetwo extracts is to be assumed.

In a randomized placebo-controlled double blank study the effectivenessof the extract prepared according to the invention was investigated in40 female patients with psychovegetative and psychosomatic disturbances.

The investigation lasted a total of eight weeks. During this time, thefemale patients were administered either 3×1 capsules of 100 mg extractor placebo.

The efficacy was assessed with the aid of the Hamilton anxiety score(HAMA). After administration of the extract prepared according to theinvention, in the fourth and eighth treatment week the HAMA score dropssignificantly (p<0.01 or 0.05), as apparent from the graphicillustration (FIG. 5). FIG. 5 depicts the HAMA-Score after theadministration (3×100 mg) of the extract produced according to theinvention and of a placebo.

I claim:
 1. Dry extract from the rhizome of Piper methysticum Forst.,wherein said extract comprises a total content of kava lactones of atleast 50% by weight and a flavokawin content of at most 0.3% by weight.2. Extract according to claim 1, comprising a total content of kavalactones of 50 to 90% by weight.
 3. Extract according to claim 2,comprising a flavokawin content of less than 0.3% by weight.
 4. Extractaccording to claim 1, comprising a total content of kava lactones of 60to 80% by weight and a flavokawin content of less than 0.2% by weight.5. A process for the preparation of a dry extract from the rhizome ofPiper methysticum Forst., comprising a total content of kava lactones ofat least 50% by weight and a flavokawin content of at most 0.3% byweight, comprising the steps of:(a) extracting the pulverized rhizome ofPiper methysticum Forst. (rhizoma kava-kava) with a first solvent toobtain an extract solution; (b) concentrating said extract solution todryness to obtain a raw extract; (c) dissolving said raw extract in asecond solvent to obtain a raw extract solution; (d) depleting thecontent of flavokawins in said raw extract solution by either coldprecipitation or solvent distribution to obtain a pure extract solution;and (e) concentrating said pure extract solution to dryness to obtainsaid dry extract having a total content of kava lactones of at least 50%by weight and a flavokawin content of at most 0.3% by weight.
 6. Theprocess according to claim 5, wherein said first solvent is chosen fromthe group consisting of: acetone, chloroform, ethyl acetate, lowalkanols having 1 to 4 C atoms, and at least 50% by weight mixturesthereof with water.
 7. The process according to claim 6, wherein saiddepleting step is accomplished by cold precipitation, and furtherwherein said cold precipitation comprising the following steps:(a)mixing said raw extract solution with water or an alkanol/water mixture;(b) cooling the mixture to 5° to 10° C.; (c) permitting the cooledmixture to stand for several hours, whereby a precipitate will bedeposited; and (d) removing the precipitate from said cooled mixture toobtain said pure extract solution.
 8. The process according to claim 6,wherein said depleting step is accomplished by solvent distribution,wherein said solvent distribution comprises distributing said rawextract solution between immiscible organic and aqueous phase, andseparating said aqueous phase from said organic phase to obtain saidpure extract solution.
 9. A dry extract prepared according to theprocess of any one of claims 5, 6, 7 or
 8. 10. A pharmaceuticalpreparation comprising the dry extract according to any one of claims 1,2, or 4, and a pharmaceutically acceptable carrier.
 11. Extractaccording to claim 1, further comprising pharmacologically inertsolubilizing matrix substances, and wherein said extract has improvedwater solubility and bioavailability after oral administration ascompared to a mixture of pure kava lactones having the same kava lactonecomposition.
 12. Extract according to claim 11, comprising between about10% and 50% by weight said matrix substances.
 13. Extract according toclaim 11, comprising about 20% by weight said matrix substances.